The present invention concerns a multidirectional mechanical device dissipating energy, particularly for the constraint of structures in seismic zones.
More particularly, the invention is referred to civil engineer structures in general, constructed in zones interested by seismic phenomenon. The solution according to the invention realizes a constraint element having the aim of dispersing the energy transmitted by the earthquake to the structure, so that the collapse of the same is avoided, greatly reducing, if not even eliminating breaking or other kinds of damages.
It is in fact well known that earthquake constitutes a release of energy stored in the underground. This energy, that reveals as shakings, is transferred to the structure and continues to shake it until it is completely dissipated. Such a dissipation, in the conventional strategy, occurs to the detriment of inner sliding in the structure.
When the structure is enough strong, said slidings are limited within little values and this does not involve a damage.
Thus, it is understood that in order to have the certainty against damages it is necessary to provide either structures extremely strong (and thus not acceptable under the economical point of view), or devices upon which the energy dissipation can be concentrated, able to control the stress transferred to the structure in such a way to avoid that it is damaged.
Otherwise, when during the time the structure gives less resistance to the earthquake action, great strains are present and consequently breaking and thus partial or total collapses.
In the field of the dissipating devices having an elastic-plastic behaviour, based on a mechanical action and a multidirectional response (i.e. a response not depending on the action direction of the external stress), the present technology, studied to reduce the structural engagement during the earthquake, basically uses elements having dimensions subjected to the ratio between the "maximum strength requested" and the "maximum corresponding movement". This choice involves big dimensions and high costs of the devices.
Among the solutions known in this field, many monodirectional solutions have been suggested.
A first solution is described in the Italian patent application N.degree. 2022A/87, concerning a "Mechanical energy and charge limiting and dissipating device, for the connection of structural elements, particularly suitable for the seismic protection of bridges, viaducts, buildings and like."
The main drawback of this kind of solution resides in the fact that it is monodirectional, so that it does not allow a dissipation on different planes, unless very complicated and bulky solutions are used.
In the Italian patent application N.degree. 47866-A/88 it is described a "Track-like mechanical device for dissipating energy" providing a solution structurally similar to the one described in the previous document, wherein the track provides inside a shape element obliging the same track to maintain the original shape when stressed.
In this case too the main drawback is due to the fact that the device is monodirectional.
Another solution is the one described in the Italian patent application N.degree. 20856-A/90, concerning a "Damper device for the seismic protection of structures like viaducts and similar."
It concerns a multidirectional device providing two C-shaped elements, having a square or round cross-section and a double symmetry.
The main drawback of this solution is due to the fact that has a very low energy absorption.
A last solution known to the Applicant is the one described in the Italian patent application N.degree. MI91A000013, describing a "Constraint device for viaducts and like.
In this solution there are noticeable constraints, since it is provided the superimposition of a plurality of plates. In order to obtain this, constraints due to the cold bending of the plates, and to the need of reducing the stretching of the same, are present, so that high thickness are necessary.
Furthermore, it is a monodirectional device.